Total sample indicator for chromatography

ABSTRACT

In a chromatographic analyzer, the carrier fluid stream is split at a point downstream from the sample injection. A first portion of the stream is passed through the chromatographic column in a conventional manner. The second portion of the stream is passed directly to the detector to provide an indication of the amount of sample injected.

United States Patent Favre [1 1 3,686,923 51 Aug. 29, 1972 [54] TOTALSAMPLE INDICATOR FOR CHROMATOGRAPHY 3,291,980 12/1966 Coates ..73/23.1X

OTHER PUBLICATIONS Investigation of the Linearity of a Stream Splitterfor Capillary Gas Chromatography, L. S. Ettre and Warren Averill,Analytical Chemistry, Vol. 33, No. 6, May, 1961, pp. 680- 684.

Primary ExaminerRichard C. Queisser Assistant Examiner-C. E. Snee, III

52 US. Cl. ..73 23.1, 23 232 C, 23 254 E I51; Int. Cl. ..G0ln 3l/08Atmmey Young and Qmgg OI [56] References Cited In a chromatographicanalyzer, the carrier fluid stream is split at a point downstream fromthe sample UNITED STATES PATENTS injection. A first portion of thestream is passed through the chromatographic column in a conveng Q BZ Htional manner. The second portion of the stream is 8 63 l x passeddirectly to the detector to provide an indica- 2 136 ;1 941364 y ag-rig4 1 tion of the amount of sample injected. 3:177:88 4/1965 Larrison..73/23.l X 10 Claims, 3 Drawing Figures 23 I3 SAMPLE H 33 2a M VALVE 32l l6 E I 3Ic:

U E 29 g 20 DETECTOR 30 3| 2| 22 l9 27 2 5 43 E MASS SPECTRQMETERPAINTEDAus29 1912 ll f CARRIER] '4 3 I 0. 3E "11 0 u 0 [I I U 23 SAMPLEL PROGRAMMER RECORDER SAMPLE VALVE 32 g l5 I 3k: 290

29 DETECTOR 3o 3 43 44 l8 MASS SPECTROMETER F IG.

m 26 g 34 35 j V 36 a K 2 TIME F IG. 2

INVENTOR.

J. Av FAVRE A T TORNEYS TOTAL SAMPLE INDICATOR FOR CHROMATOGRAPHYChromatographic analyzers have been developed in recent years which arecapable of analyzing various types of fluid mixtures. It is customary toinject a sample of the material to be analyzed into a stream of carrierfluid before the carrier fluid is introduced into the separation column.Various types of rotary and diaphragm operated sample valves have beendeveloped for this purpose. In some operations, the sample is introducedmanually by use of a hypodermic syringe. It is customary to employ oneor more signal attenuators between the detector and the recorder so thatthe recorded peaks will be of convenient height for measurement. If thecomposition of the sample should change appreciably, it may be necessaryto adjust the attenuators to maintain the desired amplitudes. In plantoperations, it is also desirable to know if the sampling system isoperating in a satisfactory manner.

In accordance with this invention, a system is provided for checking theoperation of the sampling system in a chromatographic analyzer and forproviding an indication of the amount and general composition of thesample introduced. This is accomplished by dividing the carrier fluidstream at a point downstream from the sample injection into first andsecond streams. The first stream is directed through the chromatographiccolumn to the detectorv in a conventional manner. The second stream ispassed directly to the detector so as to provide an indication of thequantity and general composition of the injected sample. The initialoutput signal from the detector, which is thus representative of thetotal sample injected, can be employed to determine proper settings ofthe attenuators for subsequent recording of the individual peaks.

In the accompanying drawing, FIG. 1 is a schematic representation of achromatographic analyzer having the sample indicator of this inventionincorporated therein. FIG. 2 is a graphical representation of the outputsignal from the detector of FIG. 1. FIG. 3 illustrates one of the streamsplitting and/or mixing devices employed in the apparatus of FIG. 1.

Referring now to the drawing in detail and to FIG. 1 in particular,there is shown a chromatographic column which contains any suitablepacking material that selectively retards passage of the constituents ofa fluid sample to be analyzed. Carrier fluid is introduced through aconduit 11 which communicates with the first inlet of a sample injectiondevice, such as a sample valve 12. A sample of the fluid mixture tobeanalyzed is introduced into valve 12 through a conduit 13. The effluentfrom sample valve 12 is passed through a conduit 14 to the first inletof a stream splitter 15. A first outlet stream from splitter 15 ispassed through a conduit 16 to the inlet of column 10. The effluent fromcolumn 10 is directed through a conduit 17 to a second stream splitter18. An outlet stream from splitter 18 is passed through a conduit 19 toa mixing device 20, and from there through a conduit 21 to the firstinlet of a detector 22. A portion of the carrier fluid passed to thesecond inlet of detector 22 through a conduit 23.

With the exception of the stream splitters and mixers, the apparatusthus far described constitutes a conventional chromatographic analyzer.Detector 22 provides an output signal which is representative of thedifference in composition of the two streams passed therethrough. Whencarrier fluid alone is passed through both channels of the detector, theoutput signal is zero. When constituents of the sample appear in thecolumn efiluent, an output signal is provided by the detector. Detector22 can advantageously be an instrument which provides an outputelectrical signal representative of this difference in composition.Instruments employing thermistors to compare thermal conductivities ofthe fluid streams and instruments employing ionization detectors areexamples of known detec tors which can be employed for this purpose.

In accordance with this invention, a second outlet stream from splitter15 is directed through a conduit 24 to the second inlet of mixer 20, andfrom there through conduit 21 to detector 22. A portion of the effluentstream from sample valve 12 is thus passed to detector 22 prior to theappearance of any of the sample constituents in the effluent from column10. This results in detector 22 providing an initial output signal whichis representative of the composition of the total sample introduced intothe analyzer. As illustrated in FIG. 2, an initial peak 26 appears inthe detector output signal which is representative of the total sample.

The output signal from detector 22 is applied through a suitableattenuation network 27 to a recorder 28. As illustrated, network 27 cancomprise a series of potentiometers 29, 30 and 31 which are connected inparallel. The contactors of these potentiometers are connected torespective output terminals 29a, 30a and 31a. A switch 32 selectivelyengages these terminals to apply an attenuated signal from the detectorto recorder 28.

Sample valve 12 and switch 32 can be controlled by a programmer 33 whichoperates the valve and the switch in timed sequence. Valve 12 isactuated at the start of the analysis cycle to introduce a sample intothe carrier fluid stream. Switch 32 can be moved to engage terminals29a, 30a and 31a in any desired sequence to provide the desired degreeof attenuation for each of the output peaks, such as 34, 35 and 36,which represent the individual constituents of the sample. The magnitudeof peak 26 provides the operator with information concerning the desireddegree of attenuation to be employed for the individual peaks in orderthat the recorder may remain on scale and still provide signals ofsuitable amplitude for detection. The presence of peak 26 also providesvisual indication of proper operation of the sampling devices.

A suitable stream splitter 15 for use in the apparatus of FIG. 1 isillustrated in FIG. 3. This stream splitter comprises a housing 40 whichprovides an interior chamber 41. Conduit 14 enters the first end ofhousing 40, and conduit 24 extends into the second end of the housing inaxial alignment with conduit 14. Conduit 16 is attached to the side wallof the housing. As illustrated, conduit 24 advantageously has a crosssectional area substantially less than that of conduit 14 so that theinlet stream is effectively divided between conduits l6 and 24. Therelative sizes of the three conduits serve to control the degree ofdivision of the inlet stream. Mixer 20 of FIG. 1 can have substantiallythe same configuration as splitter 15. In this case, conduits 19, 21 and24 correspond to respective conduits 16, 14 and 24 which are connectedto splitter 15.

In accordance with another embodiment of this invention, a portion ofthe effluent stream from column can be passed to a mass spectrometer 43to provide a detailed analysis of the column effluent. To this end,stream splitter 18 serves to divide the effluent stream from the columnand pass a portion thereof through conduit 44 to the mass spectrometer.Stream splitter 18 can have the same configuration as stream splitter15.

While this invention has been described in conjunction with preferredembodiments it should be evident that it is not limited thereto.

What is claimed is:

1. Analysis apparatus comprising:

a chromatographic column having an inlet and an outlet;

a detector adapted to provide an output signal representative of thecomposition of a fluid stream introduced therein;

a fluid stream splitter comprising a housing defining an interiorchamberand having first, second and third ports communicating with the chamber;

first conduit means communicating with said first port to introduce acarrier fluid;

sample injection means communicating with said first conduit means tointroduce a sample of material to be analyzed into said first conduitmeans;

second conduit means communicating between said second port and theinlet of said chromatographic column;

third conduit means communicating between the outlet of saidchromatographic column and the inlet of said detector; and

fourth conduit means communicating between said third port and saidinlet of said detector.

2. The apparatus of claim 1 wherein said sample injection meanscomprises a sample valve.

3. The apparatus of claim 1, further comprising a recorder, meansconnecting said detector to said recorder to apply the output signalfrom said detector to said recorder, and at least one signal attenuatingmeans included in said means connecting said detector to said recorder.

4. The apparatus of claim 3, further comprising at least one additionalsignal attenuating means, and means to connect said attenuating meansselectively in said means connecting said detector to said recorder.

5. The apparatus of claim 1, further comprising a mass spectrometer, andconduit means communicating with said third conduit means to direct aportion of 7. iii e method of claim 6, further comprising passing aportion of said second stream, after passage through the chromatographiccolumn, to a mass spectrometer.

8. The apparatus of claim 1 wherein said detector has first and secondinlets to receive fluid streams and provides an output signal which isrepresentative of a difference between the compositions of two fluidstreams passed to the respective first and second inlets thereof, saidthird conduit means communicates with said first inlet, said fourthconduit means communicates with said first inlet; and further comprisingfifth conduit means communicating between said first conduit means andsaid second inlet to pass carrier fluid to said second inlet.

9. The apparatus of claim 8 wherein said detector comprises ionizationdetectors.

10. The method of claim 6 wherein the first stream is passed to thefirst inlet of a differential detector having first and second inlets,said second stream is passed to said first inlet; and further comprisingpassing a portion of said carrier fluid to said second inlet.

1. Analysis apparatus comprising: a chromatographic column having aninlet and an outlet; a detector adapted to provide an output signalrepresentative of the composition of a fluid stream introduced therein;a fluid stream splitter comprising a housing defining an interiorchamber and having first, second and third ports communicating with thechamber; first conduit means communicating with said first port tointroduce a carrier fluid; sample injection means communicating withsaid first conduit means to introduce a sample of material to beanalyzed into said first conduit means; second conduit meanscommunicating between said second port and the inlet of saidchromatographic column; third conduit means communicating between theoutlet of said chromatographic column and the inlet of said detector;and fourth conduit means communicating between said third port and saidinlet of said detector.
 2. The apparatus of claim 1 wherein said sampleinjection means comprises a sample valve.
 3. The apparatus of claim 1,further comprising a recorder, means connecting said detector to saidrecorder to apply the output signal from said detector to said recorder,and at least one signal attenuating means included in said meansconnecting said detector to said recorder.
 4. The apparatus of claim 3,further comprising at least one additional signal attenuating means, andmeans to connect said attenuating means selectively in said meansconnecting said detector to said recorder.
 5. The apparatus of claim 1,further comprising a mass spectrometer, and conduit means communicatingwith said third conduit means to direct a portion of fluid passingthrough said third conduit means to said mass spectrometer.
 6. Themethod of analysis which comprises: introducing a sample of material tobe analyzed into a carrier fluid stream; dividing the resulting carrierfluid and sample into first and second streams; passing the first streamdirectly to the inlet of a detector which is capable of establishing anoutput signal that is representative of the composition of materialpassed thereto; and passing the second stream through a chromatographiccolumn and then to said inlet of said detector.
 7. The method of claim6, further comprising passing a portion of said second stream, afterpassage through the chromatographic column, to a mass spectrometer. 8.The apparatus of claim 1 wherein said detector has first and secondinlets to receive fluid streams and provides an output signal which isrepresentative of a difference between the compositions of two fluidstreams passed to the respective first and second inlets thereof, saidthird conduit means communicates with said first inlet, said fourthconduit means communicates with said first inlet; and further comprisingfifth conduit means communicating between said first conduit means andsaid second inlet to pass carrier fluid to said second inlet.
 9. Theapparatus of claim 8 wherein said detector comprises ionizationdetectors.
 10. The method of claim 6 wherein the first stream is passedto the first inlet of a differential detector having first and secondinlets, said second stream is passed to said first inlet; and furthercomprising passing a portion of said carrier fluid to said second inlet.